This application claims the benefit of Korean Patent Application No. 2002-23991, filed May 1, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates, in general, to an air conditioner and, more particularly, to an air conditioner with a variable capacity compressor and a method of controlling such an air conditioner.
2. Description of the Related Art
As well known to those skilled in the art, an air conditioner controls an indoor temperature by transferring heat between a refrigerant and one of indoor air and outdoor air. The air conditioner typically includes an indoor heat exchanger, an outdoor heat exchanger, a compressor, etc. During a cooling mode operation of the air conditioner, the heat is transferred from the indoor air to the refrigerant in the indoor heat exchanger and is dissipated from the refrigerant to the outdoor air in the outdoor heat exchanger so as to cool the indoor air. During a heating mode operation of the air conditioner, the refrigerant absorbs the heat generated in the outdoor heat exchanger and dissipates the heat to the indoor air at the indoor heat exchanger, thus heating the indoor air.
FIG. 1A is a block diagram showing a construction of an air conditioner having a conventional outdoor unit. As shown in FIG. 1A, the refrigerant flowing from an indoor unit 114 during a cooling mode operation of the air conditioner is introduced into a compressor 104 through a four-way valve 106. The compressor 104 compresses the input refrigerant to make high pressure and high temperature refrigerant, and discharges the refrigerant. The discharged refrigerant from the compressor 104 passes through the four-way valve 106 and flows into an outdoor heat exchanger 110. Thereafter, the refrigerant returns from the outdoor heat exchanger 110 to the indoor unit 114, and the above-mentioned cycle of the refrigerant repeats during the cooling mode operation.
The compressor 104 also contains lubricating oil therein. Therefore, during an operation of the compressor 104, a small quantity of lubricating oil is discharged from the compressor 104 together with the discharged refrigerant. In such a case, the lubricating oil discharged from the compressor 104 circulates through a refrigerant circulating line (refrigerant pipe) of the air conditioner and may reduce a heat exchanging efficiency of the outdoor and indoor units 102 and 114. Particularly, an excessive amount of the lubricating oil may be discharged from the compressor 104 during the operation to severely degrade an operational reliability of the air conditioner. Therefore, an oil separator 108, used for separating the lubricating oil from the refrigerant, is provided on the refrigerant circulating line at a position between the compressor 104 and the four-way valve 106. In such a case, a pressure of the oil separator 106 connected to an outlet port of the compressor 104 is higher than that of an inlet port of the compressor 104, and so the lubricating oil separated from the refrigerant in the oil separator 106 can be returned to the compressor 104.
In a case of a multiunit-type air conditioner with a plurality of indoor units, several compressors may be provided in the outdoor unit to meet an entire load imposed on the multiunit-type air conditioner by the indoor units. Alternatively, the multiunit-type air conditioner may be provided with a compressor having a large capacity suitable for effectively driving the entire indoor units. However, during an operation of the multiunit-type air conditioner, it is occasionally desired to operate only a part of the several indoor units. The entire load imposed on the compressor of the multiunit-type air conditioner thus varies in accordance with the number of the indoor units to be operated. Therefore, it is possible to install a variable capacity compressor in the multiunit-type air conditioner and operate the multiunit-type air conditioner while controlling a variable capacity of the variable capacity compressor in accordance with a variable load determined by the number of the indoor units to be operated.
Examples of the conventional variable capacity compressors in an air conditioner are a rotary type compressor and a reciprocating type compressor. A capacity control of the rotary type compressor is accomplished by controlling a motor speed by using an inverter. In the reciprocating type compressor with two pistons connected to a single crankshaft, a crankshaft is rotated in a forward direction or a reverse direction such that the crankshaft drives one piston set in one cylinder or two pistons set in two cylinders, thus controlling the variable capacity of the variable capacity compressor.
FIG. 1B is a view schematically showing a construction of the conventional variable capacity compressor of the reciprocating type typically used in the air conditioner. As shown in FIG. 1B, a first set of a cylinder 156a and a piston 158a forms a first compression stage of the compressor while a second set of a cylinder 156b and a piston 158b forms a second compression stage. The two pistons 158a and 158b are connected to a single crankshaft 152 and communicate with the four-way valve 106. The crankshaft 152 rotates by a motor 154, and a rotating motion of the motored crankshaft 152 is converted to a rectilinear reciprocating motion of the two pistons 158a and 158b. Of course, it should be understood that such rectilinear reciprocating motion of the two pistons 158a and 158b converted from the rotating motion may be accomplished by the use of an appropriate eccentric rotary body in place of the crankshaft 152. Due to such rectilinear reciprocating motion of the two pistons 158A and 158B, refrigerant received in the two cylinders 156a and 156b is compressed to become high pressure and high temperature refrigerant prior to being discharged from the compressor 104 to the indoor unit 114.
However, when the compressor 104 stops an operation for a lengthy period of time, liquid refrigerant remaining in the refrigerant circulating line gradually moves from the refrigerant circulating line to the compressor 104 so as to coexist with the lubricating oil in the compressor 104. In such a case, a temperature of the stopped compressor 104 is lower than that of the operating compressor 104, thus resulting in an oil separation of the lubricating oil from the refrigerant in the compressor 104, in which the refrigerant moves downward to a lower portion of the compressor 104 while the lubricating oil moves upward to an upper portion of the compressor 104. In a case of starting the operation of the compressor after the oil separation has occurred, liquid refrigerant in place of the lubricating oil may be fed to the parts of the compressor 104 during an initial stage of the operation of the compressor 104. This means that a desired amount of lubricating oil cannot be fed to the parts of the compressor and that a smooth lubricating effect of the parts may not be accomplished.
In an effort to overcome such a problem caused by the oil separation from the refrigerant, two heaters 160a and 160b may be installed at lower ends of the two cylinders 156a and 156b, respectively. The two heaters 160a and 160b heat the liquid refrigerant in the compressor 104 during the stoppage of the operation of the compressor, thus vaporizing the refrigerant, discharging the vaporized refrigerant to an outside of the compressor 104, and allowing only the lubricating oil to remain in the compressor 104.
However, the use of such heaters 160a and 160b in the compressor 104 undesirably increases a production cost and a maintenance cost of the compressor 104. Furthermore, the heaters 160a and 160b may be broken and badly affect the compressor 104. However, since the conventional compressor does not have any means for protecting the compressor from such a bad effect exerted by the broken heaters, an operational reliability of the compressor is degraded.
Accordingly, the present invention has been made keeping in mind the above and other problems occurring in the prior art, and an object of the present invention is to provide an air conditioner with a variable capacity compressor and a method of controlling such an air conditioner, in which the compressor is operated at a maximum capacity thereof in the case of starting the compressor after an extended stoppage of an operation of the compressor for a lengthy period of time longer than a preset reference time, thus increasing both a quantity of heat generated from a motor and an amount of circulated refrigerant, and so the compressor quickly discharges liquid refrigerant remaining therein to an outside of the compressor.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to accomplish the above and other objects, the present invention provides an air conditioner including a variable capacity compressor, a stop time detecting unit, and a control unit. The stop time detecting unit detects a stop time of the compressor. When the detected stop time of the compressor is longer than a preset reference time, the control unit pre-drives the variable capacity compressor at a maximum capacity for a predetermined period of time prior to operating the compressor at a required capacity to meet a load imposed on the compressor.
The present invention also provides a method of controlling such an air conditioner. The method includes pre-driving the compressor for a predetermined period of time in response to the stop time and an outdoor temperature of the compressor and normal-driving the compressor in response to a user selection.